700R4 Gear “Hunting”

[Burbinator]

So I’ve got a 91 Burb V1500. TBI 350 with a 700R4. Both rebuilt within the last 30k miles. When driving down the freeway in OD it “hunts” and struggles to pick between 3rd and 4th. Not super rapid but fast enough to be an issue. I’d say if you matched stock blinker speed, that’s how fast it switches between the two.

Is this just a TV Detent adjustment issue? Or low fluid?

 

[Ricko1966]

So I’ve got a 91 Burb V1500. TBI 350 with a 700R4. Both rebuilt within the last 30k miles. When driving down the freeway in OD it “hunts” and struggles to pick between 3rd and 4th. Not super rapid but fast enough to be an issue. I’d say if you matched stock blinker speed, that’s how fast it switches between the two.

Is this just a TV Detent adjustment issue? Or low fluid?

Find out quick, or you will need another transmission rebuild.You can check your flyid,if it's OK. You need get a transmission pressure gauge

 

[gmbellew]

Are you sure it is the 3/4 shift bouncing or is it the TCC hunting? Could be an issue with the TCC lockup solenoid?

Does the issue go away if you keep it in D?

 

[Burbinator]

Are you sure it is the 3/4 shift bouncing or is it the TCC hunting? Could be an issue with the TCC lockup solenoid?

Does the issue go away if you keep it in D?

When in what I call D3 (Not overdrive, 1-3) it doesn’t seem to. Where is that solenoid?

 

[gmbellew]

When in what I call D3 (Not overdrive, 1-3) it doesn’t seem to. Where is that solenoid?

solenoid is accessible with a pan drop. but if it doesn't hunt in D, it probably isnt the TCC lockup unless yours has been modified to not lockup in 3rd. then it could still be the solenoid if it has been changed to not lock in 3rd.

 

[bartarfonz]

A miss-adjusted Brake Switch or associated wiring can also cause Torque converter lock-up to cycle off and on as well. This could happen in 2nd, 3rd, or 4th Gear. Usually your cruise will drop out too if you have cruise control. The solenoid is in the pump and is managed by the ECM. Fluid to the convertor apply valve is managed by valve 227 in the pump and vented through the solenoid when TCC is off. When TCC is on, the Solenoid is commanded on and the fluid exhaust is blocked so a leaking solenoid can be the cause (Could be an intermittent open electrical circuit or a leaking hydraulic circuit).

 

[Burbinator]

I seem to be having issues with bad grounds. Windows, not starting, etc. Would that effect hunting gears while driving?

 

[bartarfonz]

It Could be poor grounding condition that affects the ECM and its ability to keep circuits properly managed. Also note that your comment about the misadjusted TV cable could cause it. There is also the possibility that the Cooling fan is turning on and off because of a hot engine and it sounds like the transmission is changing speeds, but it is really the cooling fan clutch turning on and off.

 

[NickTransmissions]

So I’ve got a 91 Burb V1500. TBI 350 with a 700R4. Both rebuilt within the last 30k miles. When driving down the freeway in OD it “hunts” and struggles to pick between 3rd and 4th. Not super rapid but fast enough to be an issue. I’d say if you matched stock blinker speed, that’s how fast it switches between the two.

Is this just a TV Detent adjustment issue? Or low fluid?

Have you figured out the problem as of yet?

If no, what troubleshooting and/or fixes have you tried?

How many miles on the transmission?

Bad grounds will impact your TCC control as it's electro-mechanical and commanded by the ECM which is also tied to the vehicle's electrical system. But hunting/shuttle shifting between third and fourth gear would not as the 700r4 is purely mechanical outside of the converter clutch.

Conduct a driving pressure test w/the gauge threaded in to the line pressure port on the driver's side of the transmission, just behind the bell housing (7/16 plug). See what line pressures do when shifting between third and fourth gear - particularly what's happening when it starts shuttle-shifting...Let us know and we can go from there.

Typically, falling out of fourth gear (which is technically what is happening, if you're not romping the gas or hitting the brakes) is failing 3-4 clutch pack.

 

[Burbinator]

Sorry for the late reply been super busy. Hoping this might be the problem. All the main power and ground wires look like this